The long term goal of the project is to increase understanding of the role of motilin-related peptides in the brain. The specific aims of the project are designed to provide basic information of the chemistry, distribution, biological activity, receptor binding, and release of a new neuropeptide related to porcine intestinal motilin. This basic information is vital to an understanding of motilin's interactions in the neuronal systems where it is present: the hypothalamus and Purkinje cells in the cerebellum. The location of motilin in the hypothalamus is suggestive of a role in regulation of hypothalamic function or anterior pituitary hormone release. The discovery of motilin in cerebellar Purkinje cells is of considerable interest as both a new anatomical tool for tracing Purkinje cell projections, but also as a new compound which could influence functioning of the Purkinje system. Thus motilin may be intimately involved in the complex tasks performed by the cerebellum and may be of considerable clinical significance. The specific aims of the proposed research are: 1) Using HPLC and other chromatographic methods motilin related peptide will be pruified from rat brain for amino acid composition and sequence analysis. The biological activity of this material will be tested with a new dispersed cell preparation of guinea pig smooth muscle cells and the conventional handing gut strip bioassay in comparison with porcine motilin and motilin fragments. 2) The binding of 125-I labeled motilin to rat brain synaptosomes will be studied utilizing standard radioreceptor techniques and the microscopic distribution of motilin binding sites will be determined with receptor autoradiography methods. The ability of porcine motilin, motilin fragments, and purified rat brain motilin to inhibit binding will be tested. 3) The projections of motilin-containing Purkinje neurons to the deep cerebellar nuclei and the motor nuclei of the brainstem will be studied utilizing knife cuts, motilin immunocytochemistry, and motilin RIA. 4) The effect of motilin and motilin fragments on the uptake and release of 3H GABA from cerebellar slices and synaptosomes will be studied. The release of motilin from cerebellar slices will be studied to determine if GABA or norepinephrine modulate basal or stimulated release motilin.